Backpack



FIG. 1 is a front, left perspective view of a backpack showing my new design;

FIG. 2 is a front view thereof;

FIG. 3 is an enlarged view of FIG. 2 with unclaimed subject matter omitted;

FIG. 4 is an alternate configuration of the front perspective view thereof; and,

FIG. 5 is a front view of FIG. 4 thereof.

The uneven-length broken lines immediately adjacent to the shaded area represent unclaimed boundaries of the design. The unshaded regions within the shaded area that are demarcated in part by uneven-length broken lines form no part of the claimed design. The even-length broken lines showing the remainder of the backpack are for environmental purposes only and form no part of the claimed design. 

CLAIM The ornamental design for a backpack, as shown and described. 